In Which I Learn to Loft

Keel, stem and bottom parts.

Keel, stem and bottom parts.

I would like to emulate Captain Joshua Slocum, who followed the tradition of ancient boat builders when he set about rebuilding Spray before his solo journey around the world in 1899. “My ax felled a stout oak-tree near by for a keel,” he wrote in the opening pages of his narrative, “and Farmer Howard, for a small sum of money, hauled in this and enough timbers for the frame of the new vessel.” But I don’t have a woodlot, or a farmer Howard, so my ax fell to the lumberyard and, for a $35 delivery charge, several sixteen foot long 1 x 12 boards were delivered the next day. In my more humble craft, the keel is not cut from a single piece of timber, as is tradition. Instead, it is assembled from four pieces of number two pine, laminated together with screws and glue to create a single 1 ½ inch thick keel. The illustration from the Pocket Cruiser’s plans illustrates the general principal.

Still, the work seems challenging enough. Indeed, I am about to get my first true lesson in the arcane art of boat building.

In carpentry, most lines are straight and measurements are easy. Tape measures and T-squares assure complete accuracy. The only degree that matters is 90 degrees. In boat building, however, nothing—absolutely nothing—is straight or 90 degrees. Every line is curved or angled. As I examined the plans for the keel, I began to fully appreciate this fundamental difference. The boat’s spine is like a snake that just ate a mouse; it not only follows a gentle curve, but also grows wider in the middle before narrowing again at the stem. Somehow, I have to accurately draw all of these curving lines onto my pine boards.

There are two ways to do this. The easy way employed by some boat designers is to print full size plans. Builders simply trace the pattern onto the boards, like a seamstress tracing a pattern for a shirt or dress on fabric. The traditional (and harder way) employs a skill unique to boat builders called “lofting.” Unfortunately, my project takes that harder way. It sends shivers of anxiety down my spine.

Like so many arcane nautical terms, “lofting” has an aura of Old World complexity. I was familiar with the term and vaguely understood that it was a necessary first step in the boat building process. But I viewed lofting as an art, something handed down from master to apprentice, a secret held by those within the guild. I don’t know where I got this idea. Maybe it was my insecurity as a boat builder; maybe I was responding to an attitude among a certain class of boat builders who do, in fact, try to shroud their work with an aura of magic and mystery. In either case, it was an enormous psychological barrier.

But it only took a few minutes of examination to realize that lofting the Pocket Cruiser is, in fact, a simple and straightforward process. “Lofting” simply means copying a pattern onto the wood. It takes time, but it’s not hard and, I discovered, it’s possible to do with a fair amount of precision.

The first step is to draw a centerline down the length of the wood. Next, a simple grid is created by drawing a series of evenly spaced lines perpendicular to the centerline. These are called “station lines.” To copy the keel’s shape onto the board, I simply drive two nails in each station line, one above and one below the centerline. These measurements are called “offsets.” The Pocket Cruiser’s plans tell me exactly how far above and below the centerline each offset is located.

For example, the first station line requires a nail 4 inches above and 5 inches below the centerline. This means that, at that station line, the keel in 9 inches wide. At the second station line, I place a nail 3 inches above and 5 ½ inches below the station line. This simple process is repeated along 14 station lines, each spaced 12 inches apart.

Here’s the fun part. After all nails are driven, I take a long, thin piece of wood—a batten—and push it against the line of nails. Instantly, the keel’s gentle inward curve is revealed as the batten pushes against each protruding nail. I look for mistakes in my measurements, which would be indicated by a bump or divot, but it looks pretty good. So with help from Matthew, my youngest son, I take a pencil and trace both the top and bottom curves of the keel. It’s like connect the dots, and just as fun.

Following the same process, I loft the boat’s stem from a shorter piece of wood. This will project upward at the boat’s bow.

Nails mark offsets in the stem (bottom left) and the keel (top right)

Nails mark offsets in the stem (bottom left) and the keel (top right)

These two pieces produce half of the keel. To create the full 1 ½ inch thick keel, I need to cut another keel bottom and stem. Now that I have a template, I don’t need to repeat the lofting process. I simply lay the pieces on top of pine boards and trace the pattern. The only variation is that the second keel half is cut a bit shorter in the front and the stem is cut a bit longer. This allows boards to overlap, creating a surface for gluing and fastening all four pieces.

The final step is cutting. I set my circular saw blade a fraction of an inch deeper that the boards I am cutting. Next, I lay the boards on pieces of scrap 2 x4 and, working with great care, slowly follow the curving lines of the keel. It’s a new experience purposely cutting curves with a circular saw; as a carptenter, I’m usually trying to keep my cuts straight. But I discover that it’s possible to cut gentle arcs without binding the blade if I move slowly. In short order, I have all four parts of the keel laying on the garage floor.

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